The present invention relates to a tubeformed rock bolt. More specifically the invention concerns a tubeformed rock bolt which is formed for being joined to arbitrary length.
In a previously known rock bolt of the above mentioned kind, see U.S. Pat. No. 4,509,889, one can achieve a long rock bolt through entering a rock bolt into a bore hole and expanding it. Then a further bolt is entered on a tube extending from the inner rock bolt and is expanded so that it is fixed on the extending tube. A drawback when setting a long rock bolt comprising several short rock bolts is that one needs a long tool which normally must be bendable in order to set the rock bolt which is to be innermost in the bore hble. Another drawback is that the rock bolt at the joints becomes substatially weaker since the connection is obtained through friction. This force becomes small because the extending tube has small diameter and thus a small outer surface.